What is a watt in simple terms?

A watt is a unit of power that measures the rate of energy transfer. One watt equals one joule of energy per second. A 100-watt light bulb uses 100 joules of energy every second.

How do watts relate to volts and amps?

Watts = Volts × Amps. This is known as the power equation. A device drawing 5 amps from a 120-volt outlet uses 600 watts of power.

What is the difference between watts and watt-hours?

Watts measure power (rate of energy use), while watt-hours measure energy (total amount used). A 100W bulb running for 10 hours uses 1,000 Wh (1 kWh) of energy. Power is like speed; energy is like distance.

What Is a Watt? Definition, History & Everyday Examples

Definition

A watt (symbol: W) is the SI unit of power, defined as one joule of energy per second:

1 W = 1 J/s = 1 kg·m²/s³

Power measures how quickly energy is used or produced. A higher wattage means energy is being consumed or generated faster.

The Power Triangle

For electrical circuits, three key relationships connect watts, volts, and amps:

Watts = Volts × Amps (P = V × I)
Watts = Volts² ÷ Ohms (P = V²/R)
Watts = Amps² × Ohms (P = I²R)

Everyday Wattage Examples

Device	Typical Wattage
LED light bulb	8-15 W
Laptop computer	30-65 W
Television	50-200 W
Refrigerator	100-400 W
Microwave oven	600-1,200 W
Hair dryer	1,000-2,000 W
Electric oven	2,000-5,000 W
Electric car charger (Level 2)	7,200-19,200 W

Watts vs Watt-Hours

Watts measure power (rate); watt-hours measure energy (total amount). Think of it like speed vs distance:

A 100W bulb running for 1 hour uses 100 Wh = 0.1 kWh
A 1,000W heater running for 3 hours uses 3,000 Wh = 3 kWh
Your electricity bill charges per kWh, not per watt

History

The watt is named after James Watt (1736-1819), the Scottish inventor who improved the steam engine. Ironically, Watt himself used the term "horsepower" to market his engines. The watt was adopted as the SI unit of power in 1960. One horsepower equals approximately 746 watts.

Common Watt Multiples

Prefix	Symbol	Value	Example
Milliwatt	mW	0.001 W	Laser pointer
Watt	W	1 W	Small LED
Kilowatt	kW	1,000 W	Space heater
Megawatt	MW	1,000,000 W	Wind turbine
Gigawatt	GW	10⁹ W	Power plant

Convert between power units with our power converter.